I. Field of the Invention:
This invention relates generally a method of fabricating guide catheters, and more particularly to a method for securing the proximal hub to the catheter body without causing delamination of a Teflon lining of the catheter's lumen.
II. Discussion of the Prior Art:
A guide catheter comprises an elongated tubular member which may be inserted through an incision and routed through a vein or artery to a desired site, and then an angiography catheter or an angioplasty catheter of a smaller cross-sectional dimension may be routed through the guide catheter to the location where a dye or other medicament is to be injected or where an angioplasty procedure is to be carried out on a stenotic lesion. To facilitate the movement of the angiography catheter or the angioplasty catheter within the lumen of the guide catheter, it has been found convenient to line the lumen of the guide catheter with a thin Teflon layer because of the low coefficient of friction possessed by the Teflon material. The guide catheter itself typically comprises an elongated tube formed from a suitable thermoplastic material, such as polyethylene, and which may have reinforcing braid incorporated within the side walls and which is disposed about the thin Teflon liner. The hub may be a molded plastic part which has a central bore formed longitudinally therethrough and terminating internally in a counterbore of a lesser diameter extending inwardly from the distal end thereof and terminating in an annular shoulder. The diameter of the counterbore is only slightly larger than the outside diameter of the catheter body stock to which it is to be attached.
In the past, serious problems were encountered when an attempt was made to bond the hub to the proximal end of the catheter body stock. Specifically, the Teflon lining, because of its unique properties, is difficult to adhesively bond to the inner walls of the braid-reinforced polyethylene catheter body. Thus, there has been a tendency in the prior art for the Teflon lining to delaminate to the extent that it would block the lumen of the guide catheter. Thus, while the plastic hub can readily be bonded to the thermoplastic exterior of the catheter body stock, it has been necessary to devise a way for preventing the delamination of the Teflon liner covering the lumen of the thermoplastic tubular catheter.
The Diettrich U.S. Pat. No. 3,720,210, the Bodicky U.S. Pat. No. 4,354,495 and the Czuba et al U.S. Pat. No. 4,391,029 each describe ways of securing a molded plastic hub to the proximal end of a catheter body. In the Diettrich patent, the catheter body itself is made from polytetrafluoroethylene (Teflon) and is provided with an integral flange at one end and an additional outer tubular member or sleeve of a different plastic material, and the tube end and sleeve are insert molded in a hub member. Typical guide catheters, however, cannot be fabricated from a Teflon material because it is too rigid and inflexible if of a thickness to serve as the catheter body stock itself. It is for this reason that a stainless steel braid reinforced plastic with a Teflon lining to provide a low friction internal surface has worked so well. The flexibility and torque characteristics of the resulting catheter are dictated primarily by the outer plastic and the embedded blade while the Teflon lining is sufficiently thin as not to seriously increase the rigidity of the resulting catheter.
One drawback to this catheter construction has been the tendency of the thin Teflon lining to delaminate from the surrounding catheter body stock. The insertion of various working catheters through the lumen of the guide catheter and/or the introduction of fluids through the guide catheter has caused the Teflon lining to, at times, peel away from the surrounding tubular walls of the catheter's body stock. The present invention describes a method for bonding a hub to a Teflon-lined catheter in such a fashion that this delamination is prevented.